A5031023643- Stellar, planetary, and galactic studies
- Astrophysics and Star Formation Studies
- Astronomy and Astrophysical Research
- Astro and Planetary Science
- Astronomical Observations and Instrumentation
- Gamma-ray bursts and supernovae
- Astrophysical Phenomena and Observations
- Atmospheric Ozone and Climate
- Planetary Science and Exploration
- Galaxies: Formation, Evolution, Phenomena
- Spectroscopy and Laser Applications
- Solar and Space Plasma Dynamics
- Space Exploration and Technology
- History and Developments in Astronomy
- Calibration and Measurement Techniques
- Experimental and Theoretical Physics Studies
- Scientific Research and Discoveries
- Ionosphere and magnetosphere dynamics
- Historical Astronomy and Related Studies
- Atmospheric aerosols and clouds
- CCD and CMOS Imaging Sensors
- Molecular Spectroscopy and Structure
- Adaptive optics and wavefront sensing
- Inertial Sensor and Navigation
- Space Satellite Systems and Control
University of Denver
2014-2023
Kyoto University
2021-2022
Japan Aerospace Exploration Agency
2014
Institute of Space and Astronautical Science
2014
Des Moines University
2014
Rochester Institute of Technology
2011
Ames Research Center
2005-2008
Royal Observatory of Belgium
2002-2008
National Postdoctoral Association
2006
University of Illinois Urbana-Champaign
1998-2004
We are performing a uniform and unbiased, ~7x7 degrees imaging survey of the Large Magellanic Cloud (LMC), using IRAC MIPS instruments on board Spitzer Space Telescope in order to agents galaxy's evolution (SAGE), interstellar medium (ISM) stars LMC. The detection diffuse ISM with column densities >1.2x10^21 H cm^-2 permits detailed studies dust processes ISM. SAGE's point source sensitivity enables complete census newly formed masses >3 solar that will determine current star formation rate...
We present ∼1000 new candidate Young Stellar Objects (YSOs) in the Large Magellanic Cloud selected from Spitzer Space Telescope data, as part of Surveying Agents a Galaxy's Evolution (SAGE) Legacy program. The YSOs, detected by their excess infrared (IR) emission, represent early stages evolution, still surrounded disks and/or infalling envelopes. Previously, fewer than 20 such YSOs were known. SAGE Point Source Catalog regions color–magnitude space least confused with other IR-bright...
Color-magnitude diagrams (CMDs) are presented for the Spitzer SAGE (Surveying Agents of a Galaxy's Evolution) survey Large Magellanic Cloud (LMC). IRAC and MIPS 24 μm epoch 1 data presented. These represent deepest, widest mid-infrared CMDs their kind ever produced in LMC. Combined with Two Micron All Sky Survey, used to delineate evolved stellar populations LMC, as well Galactic foreground extragalactic background populations. Some 32,000 stars brighter than tip red giant branch identified....
The goal of this paper is to present the results a preliminary analysis extended infrared (IR) emission by dust in interstellar medium (ISM) Large Magellanic Cloud (LMC). We combine Spitzer Surveying Agents Galaxy Evolution (SAGE) and Infrared Astronomical Satellite (IRAS) data correlate with gas tracers H i, CO, Hα. global as well detailed modeling spectral energy distribution (SED) few selected regions. Extended associated neutral, molecular, diffuse ionized phases ISM detected at all IR...
Far-infrared Herschel/PACS images at 70 and 160 micron of a sample 78 Galactic evolved stars are used to study the (dust) emission structures, originating from stellar wind-ISM interaction. In addition, two-fluid hydrodynamical simulations coupled gas dust in interactions compare with observations. Four distinct classes interaction (i.e. "fermata", "eyes", "irregular", "rings") identified basic parameters affecting morphology discussed. We detect bow shocks for ~40% detached rings ~20%....
MESS (Mass-loss of Evolved StarS) is a Guaranteed Time Key Program that uses the PACS and SPIRE instruments on board Herschel Space Observatory to observe representative sample evolved stars, include asymptotic giant branch (AGB) post-AGB planetary nebulae red supergiants, as well luminous blue variables, Wolf-Rayet stars supernova remnants. In total, order 150 objects are observed in imaging about 50 spectroscopy. This paper describes target selection list, observing strategy. science...
We report the results from an optical imaging survey of proto-planetary nebula candidates using Hubble Space Telescope (HST). The goals were to image low surface brightness reflection nebulosities around nebulae and investigate distribution circumstellar dust, which scatters star light central post-asymptotic giant branch creates nebulosities. exploited high resolving power wide dynamic range HST detected in 21 27 sources. reduced deconvolved images are presented along with photometric...
We present an overview of the initial results from Chandra Planetary Nebula Survey (ChanPlaNS), first systematic (volume-limited) X-ray Observatory survey planetary nebulae (PNe) in solar neighborhood. The phase ChanPlaNS targeted 21 mostly high-excitation PNe within ~1.5 kpc Earth, yielding 4 detections diffuse emission and 9 X-ray-luminous point sources at central stars (CSPNe) these objects. Combining with those obtained archival data for all (14) other that have been observed to date, we...
We present the data from a mid-infrared (MIR) imaging survey of 66 proto-planetary nebula candidates using two MIR cameras (MIRAC2 and Berkcam) at NASA Infrared Telescope Facility United Kingdom Telescope. The goal this is to determine size, flux, morphology emission regions, which sample inner regions circumstellar dust shells nebulae. imaged these nebulae with narrowband filters(Δλ/λ~10%) wavelengths notable features. With our typical angular resolution 1'', we resolve 17 sources, find 48...
We present X-ray spectral analysis of 20 point-like sources detected in Chandra Planetary Nebula Survey observations 59 planetary nebulae (PNe) the solar neighborhood. Most these detections are associated with luminous central stars within relatively young, compact nebulae. The vast majority X-ray-emitting at PN cores display "hard" (⩾0.5 keV) emission components that unlikely to be due photospheric from hot (CSPN). Instead, we demonstrate well modeled by optically thin thermal plasmas. From...
We have developed a general purpose dust radiative transfer code for an axisymmetric system, 2-DUST, motivated by the recent increasing availability of high-resolution images circumstellar shells at various wavelengths. This solves equation following principle long characteristic in two-dimensional polar grid while considering three-dimensional radiation field each point. A solution is sought through iterative scheme which self-consistency achieved requiring global luminosity constancy...
The results of a Hubble Space Telescope (HST) snapshot survey post-AGB objects are shown. aim the is to complement existing HST images protoplanetary nebulae and connect various types nebulosities with physical chemical properties their central stars. Nebulosities detected in 15 33 sources. Images photometric geometric measurements presented. For sources we see morphological bifurcation into two groups, DUPLEX SOLE, as previous studies have found. We find further support for results,...
The detected variety in chemistry and circumstellar shell morphology of the limited sample Galactic post-AGB stars is so large that there no consensus yet on how different objects are linked by evolutionary channels. evaluation complicated fact their distances hence luminosities remain largely unknown. Via cross-correlation Spitzer SAGE catalogue with optical catalogues we selected a LMC candidates based [8]-[24] colour index estimated luminosity. We determined fundamental properties central...
CW Leo has been observed six times between October 2009 and June 2012 with the SPIRE instrument on board Herschel satellite. Variability detected in flux emitted by central star a period of 639 \pm 4 days, good agreement determinations literature. is also bow shock around that had previously ultraviolet PACS/SPIRE data. Although difficult to prove directly, our working hypothesis this variability directly related star. In case, fitting sine curve fixed days results time-lag 402 37 days. The...
We present results from the most recent set of observations obtained as part Chandra X-ray observatory Planetary Nebula Survey (ChanPlaNS), first comprehensive survey planetary nebulae (PNe) in solar neighborhood (i.e., within ~1.5 kpc Sun). The is designed to place constraints on frequency appearance and range spectral characteristics X-ray-emitting PN central stars evolutionary timescales wind-shock-heated bubbles PNe. ChanPlaNS began with a combined Cycle 12 archive 35 continued via 14...
We present new observations of the ionized gas, molecular and cool dust in Helix Nebula (NGC 7293). The gas is observed form an Hα image, which constructed using images from Southern Sky Survey Atlas. emission was mapped H2 v = 1 → 0 S(1) line at 2.122 μm. far-infrared (FIR) were obtained ISOPHOT on Infrared Space Observatory. are more sensitive than previous measurements show huge extent Helix, confirming it as a density-bounded nebula showing previously unseen point-symmetric structures....
We present the first results of MIRIAD (MIPS [Multiband Imaging Photometer for Spitzer] Infra-Red AGB [asymptotic giant branch] Dustshells) project using Spitzer Space Telescope. The primary aim is to probe material distribution in extended circumstellar envelopes (CSE) evolved stars and recover fossil record their mass loss history. Hence, we must map whole CSEs plus surrounding sky background subtraction, while avoiding central star that brighter than detector saturation limit. With our...
Abstract We present $10$$\times$50scan maps around an M supergiant $\alpha $ Ori at 65, 90, 140, and 160$\mu$m obtained with the AKARI Infrared Astronomy Satellite. Higher spatial resolution data exact analytic solution permit us to fit de-projected shape of stellar-wind bow shock have a stand-off distance $4\farcm8$, position angle 55$^{\circ}$ inclination 56$^{\circ}$. The suggests that velocity respect local medium is $v_* = 40n_{\rm H}^{-1/2}$, where $n_{\rm H}$ hydrogen nucleus density...
<i>Herschel<i/> PACS and SPIRE images have been obtained of NGC 6720 (the Ring nebula). This is an evolved planetary nebula with a central star that currently on the cooling track, due to which outer parts are recombining. From we conclude there striking resemblance between dust distribution H<sub>2<sub/> emission, appears be observational evidence forms grain surfaces. We developed photoionization model Cloudy code used determine physical conditions investigate possible formation scenarios...
We present far-infrared and submillimetre spectra of three carbon-rich evolved objects, AFGL 2688, 618 NGC 7027. The were obtained with the SPIRE Fourier-transform spectrometer on board <i>Herschel<i/> Space Observatory, cover wavelengths from 195–670 <i>μ<i/>m, a region electromagnetic spectrum hitherto difficult to study in detail. far infrared these objects are rich complex, we measure over 150 lines each object. Lines due 18 different species detected. determine physical conditions...
This is the first of a series investigations into far-IR characteristics 11 planetary nebulae (PNs) under Herschel Space Observatory Open Time 1 program, Planetary Nebula Survey (HerPlaNS). Using HerPlaNS data set, we look PN energetics and variations physical conditions within target nebulae. In present work, provide an overview survey, acquisition processing, resulting products. We perform (1) PACS/SPIRE broadband imaging to determine spatial distribution cold dust component in PNs (2)...
We perform a comprehensive analysis of the planetary nebula (PN) NGC6781 to investigate physical conditions each its ionized, atomic, and molecular gas dust components object's evolution, based on panchromatic observational data ranging from UV radio. Empirical nebular elemental abundances, compared with theoretical predictions via nucleosynthesis models asymptotic giant branch (AGB) stars, indicate that progenitor is solar-metallicity, 2.25-3.0 Msun initial-mass star. derive best-fit...
We use detailed radiative transfer models to investigate the differences between star-obvious low-level elongated proto-planetary nebulae (SOLE PPNs) and dust-prominent longitudinally extended (DUPLEX PPNs), which are two subclasses of PPNs suggested by Ueta, Meixner, & Bobrowsky. select one SOLE PPN, HD 161796, DUPLEX IRAS 17150-3224, both well studied representative their PPN classes. Using an axisymmetric dust shell code, we model these sources in detail constrain mass-loss histories,...
<i>Herschel<i/> PACS and SPIRE images have been obtained over a 30' × area around the well-known carbon star CW Leo (IRC +10 216). An extended structure is found in an incomplete arc of ~22' diameter, which cospatial with termination shock due to interaction interstellar medium (ISM) as defined by Sahai & Chronopoulos from ultraviolet GALEX images. Fluxes are derived 70, 160, 250, 350, 550 <i>μ<i/>m bands region where ISM takes place, this can be fitted modified black body temperature 25...